you need to write an extension for that. This extension would add a button to the stage which toggles an internal variable (can be persisted through the engine) when clicked and if the variable is on, then a timer is set which moves the game to the next line. You probably want this to work for every time when a click is normally needed, not only for lines, right? Then you should listen to the event "wse.interpreter.next.after.nonext" on the game's bus.

It might be a good idea to have a different autoplay wait time depending on the length of a line's content so that a user has enough time to read what's displayed. To do that you will have to differentiate between a "nonext" event triggered after a line command versus a "nonext" event triggered after another command.

You can do this by having a variable in your extension and listening to the line command's event: